Rear Seal

[QUOTE='musty 4.6L]long story short, my rear seal from tranny to driveshaft slid off, lots of fluid leakage, put old one back on ( don't ask (, came off 2 weeks later, bought a new one from napa, haven't installed it yet, MY QUESTION IS.

Why in the hell is it coming off??! too much fluid in tranny? this seems to happen when going fast on a hill or something inclined , any ideas?[/QUOTE]
If you have between 3.5 and 4 quarts of fluid in the tranny, that is normal. You might want to put some thread locker on there as well (the one in the blue bottle).. I have no experience with changing the rear seal, but just trying to throw some stuff out there. any gaskets you could replace?